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Name: Natalie
Status: Educator
Grade:  9-12
Location: IN
Country: United States
Date: February 2007

What is the easiest way to teach students the difference between codominance and incomplete dominance? They always confuse them.

Codominance - A form of inheritance in which both alleles are equally shown.

Blood typing is a great example.
AB blood is the codominant relationship between the A protein and B protein both expressing themselves completely.
AO (type O allele means there is no protein), A is dominant and you see type A phenotype.
BO is the same except you see the B phenotype. Type O is recessive.

Incomplete dominance - A form of inheritance in which the heterozygous alleles are both expressed, resulting in a combined phenotype.

The one example that most books give is seen in some flower colors.
A red and a white allele gives pink. If it were codominance, you would see the red and white colors.
Incomplete dominance is most commonly found in plants.

Steve Sample

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